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Discussion Starter #1
Hey,

So I recently noticed that my car was making a clicking sound when I opened the doors. No, it's not the lock. It's not the shift lockout. It makes a series of clicks up under the dash. When I first noticed it, I posted a video where you could hear it and a helpful poster (on FB) thought it might be one of the three HVAC actuators. For the record, it might click 5-6 times, but sometimes it goes 20-30 before stopping.

I took it over to my local dealer and they told me it was actually the 'brake actuator'. When describing the symptoms to them originally, I had only noticed that morning that the clicks always stopped when you put your foot on the brake. The service guy told me that GM was aware of the issue with the brake actuator and no solution was yet available. According to the service guy, this is harmless. I never consider an issue with the brakes 'harmless'. If the actuator is rotating needlessly or whatever it controls is slamming against the stops repeatedly, this will eventually lead to a failure of some sort -- again, this is the ABS brake system so is that failure catastrophic?

Does anyone else notice a clicking sound in or under the dash when you enter your Bolt (even from passenger side, or rear hatch, with key fob)? Did GM diagnose your issue? Did they provide a solution? The service guy mentioned a bulletin on it but did not give me a number or other identifying information so I could track it. So I don't really have a way to track GM's progress on a solution.

Anyone else have a Bolt that talks to them when they open the doors or hatch? Thanks in advance
 

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Hey,

I took it over to my local dealer and they told me it was actually the 'brake actuator'.
It is the Bosch i-Boost power assist unit for the brakes. There is a tooth broken out of the gear rack on the side of the master cylinder unit. I don't know how unsafe it is, but it is broken and should be replaced under warranty. Your dealer is incompetent. Call GM!
 

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Discussion Starter #3
Thanks, I was trying to figure out what it was called. Appreciate the info. I'll be talking to the dealer (again) and I have no false sense of security about the competence of the GM dealers in my area.
 

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Discussion Starter #6
Yeah, I found it. It has a helpful sticker that reads iBooster with several multi-digit numbers. I read Bosch's information on it and realized that it played a bigger role in the operation of my vehicle. The Bosch material says that it pressurizes the hydraulic system and helps balance the regenerative and friction braking of the vehicle. This is an interesting point.. Several weeks ago, I noticed a drop in the aggressiveness of my regenerative braking system such that I was using the paddle more. When you learn the deceleration curve of the vehicle and then you have to relearn it because it changed.. very strange. The video seems to support the written information I have.. that this iBooster actually participates in both regenerative and friction braking.

Rather than poke around with the mooks at my local dealer, I dropped a dime to GM Customer Care and explained the situation. If I die in a fiery crash now, there are records at both the dealership and national level about my concerns with the safety of the vehicle.

Who knows.. maybe I am going a little crazy listening to that clicking and the braking is working just fine. But if I am right, and it results in any damage, GM will be holding the bag (assuming I survive)
 

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Mine just was replaced, under warranty. I Booster Bosch Brake Module, now quiet vehicle with no more low thumping sound at rest.
GM Bolt Central is well aware of this problem; dealers not so much.
 

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Thanks for the helpful thread. There are more reports of the same issue at insideevsforum.com. It may be a more widespread issue than GM or others realize, so I thought it might be helpful for me to report I have this identical problem. Perhaps it is worth a recall, or at least a service bulletin?

Also would appreciate any dealer recommendations in Northern California. Not sure I'm getting the best service possible from mine.
 

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Discussion Starter #11
Hey Bill,

I emailed you a link to a pair of video clips that you should be able to review and share with them. As far as I know (I'm just a consumer), there is no public TSB or recall on this yet but I personally have read or otherwise communicated with at least 5-6 Bolt owners that have or are experiencing the same thing. In my case, they replaced the iBooster (actually the master cylinder assembly and brake pedal assembly) and I think they might have done a small software update. It works great now, so I'm happy.

In the bigger picture, I think I am a typical Bolt owner with a 2017 (late August) that has 16000 miles on it. I drive mostly in L, use brakes infrequently, and do 70/30 surface vs highway driving. I probably press the brake pedal a few times a day but no more than two or three per drive in normal operation. So I don't think I did anything to precipitate this. I also wonder if more owners are living with it as a 'normal' thing since the first dealer I took it to told me 'no error codes, that sound is perfectly normal'.

Anyway, good luck getting the repair. That part is hard to get and took about 6 weeks to arrive.. and only two hours to install.

Mike
 

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2017 Chevy Volt has same problem, repeatedly

I live on Kona side of Big Island. Dealer is 2 hour drive down mountain to Hilo side, each way. I have had the entire brake assembly replaced twice, but noise keeps returning. GM Customer Care is awful (they seem clueless on anything technical), as is Dealer. The only mechanic certified on Chevy electric vehicles (who has done the first 2 replacements told me he replaces brake assembly often on both Bolts and Gen 2 Volts for this reason, yet GM Customer Care claims they have no other alerts on Regen Braking assembly). The actuator makes this clicking noise once you activate electronics in car (open door, use FOB). It is loud and lasts until you start using brake pedal. If brakes are hot, the actuator won't make clicking noise. That means I must wait a couple hours before proving to Dealer that the problem has returned, whihc forces me to stay overnight in Hilo.

I had to drive it over again and rent hotel, as Gm insisted. Now, I will return later thsi month to try my third repalcment of brake assembly. I have run up large hotel bills on several trips to get this fixed. Given the history, I dont think GM will be able to fix it. No one would ever buy my car when I explain to them that the nosie is do to design defect in brake assembly that appears to not be amenable to repair. Has anyone filed a lemon claim because of this problem.

PS: I wont let my wife drive car because we live on side of volcano, with heavy need for brakes. She is not a great driver and would freak out if brakes failed on the mountain. As result, we have driven the car very little. I have bought many GM cars. I am really impressed by the Volt technology. But, this brake problem is serious and GM cant seem to fix it, as actuator noise returns within 2 months of replacing the entire assembly. Has anyone else had success with installing a new assembly? Very unhappy with this car
 

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The electric power brake booster is made by Bosch. GM doesn't make them. They are dependent on their supplier

As for worrying about coming down the mountains with a failing brake booster, the hydraulic brakes on this car will work without boost, just requiring greater pedal pressure. But, in fact, this is the safest car you can buy for driving in the mountains.
You should be driving in L, and using the paddle. This is a totally separate system from the hydraulic brakes, and allows driving in the most mountainous conditions without ever using the brakes at all, while recouping energy.
 

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It is the Bosch i-Boost power assist unit for the brakes. There is a tooth broken out of the gear rack on the side of the master cylinder unit. I don't know how unsafe it is, but it is broken and should be replaced
Hi Gjetson,
how do you know it is a tooth broken?
Have you seen it broken?
Maybe you could share the picture of it broken if available?
From what I found it seems not too big deal to change the gear. Am I right? If yes maybe you could advice on where to get the spare parts for the booster?

I have exactly the same problem with the same symptoms on my 2016 Volt which is out of the warranty. It started to make this noise recently, brakes work as supposed to, just the noise is annoying.
 

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Hi Gjetson,
how do you know it is a tooth broken?
Have you seen it broken?
Maybe you could share the picture of it broken if available?
From what I found it seems not too big deal to change the gear. Am I right? If yes maybe you could advice on where to get the spare parts for the booster?

I have exactly the same problem with the same symptoms on my 2016 Volt which is out of the warranty. It started to make this noise recently, brakes work as supposed to, just the noise is annoying.
From the symptoms described when this problem cropped up several years ago on the Bolt forums. If you understand how a rack and pinion system function, it was pretty likely it was a tooth out in the rack. At some point I seem to recall this was confirmed by somebody. The master cylinder piston must return to its home position for the stepper motor to stop. A tooth missing on the pinion would not prevent that. A tooth missing in the rack could. The fact that you can depress the pedal, moving the rack slightly, and get the piston to return to its home position suggest this is the problem.

As to getting replacement parts for the brake booster...I would be amazed. There was a time when you could get replacement electrodes, and ceramic insulators for rebuilding spark plugs. That is not the world we live in.


It appears GM offers no parts breakdown, but check at the parts desk of your local dealer. Then check salvage yards on the internet.
 

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Yes most probably you are right. However I found some strange facts:
1) in one of the frorum threats Bolt owner had his iBooster replaced twice and the problem came back soon. Then it would mean that both replacements were taken from the same defective batch?
2) the iBooster ticking problem was typical to 2014 Tesla, however at speeds above 25 mph. For some owners their dealers also went with the booster replacement. However in January 2015 Tesla issued a software/firmware update 2.2.115 and the ticking disappeared (the link in here).
3) another Bolt owner told that besides iBooster replacement his dealer did as well some update. Nobody else in the Bolt/Volt forums told that or nobody knew they received an update.

So I do not reject that the clicking/ticking noise from the iBooster is coming due to software/firmware which might be forcing for some reason the stepper motor to continue working AFTER master cylinder piston has returned to its home position thus making the noise. But this is my guess.

If master cylinder piston has not returned to its home position then we could see the brake lights always on. I just experienced and fixed such issue combined with Service Stabilitrak + BRAKE red light + booster temporarily not working at all. I thought I found the issue but now I'm in doubts again. If the iBooster tooth had separated it could stuck in between gears and cause all the problems I had. The booster clicking noise appeared afterwards, it was not there before. Here is the link to the problem and my fix.
 

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1) in one of the forum threads Bolt owner had his iBooster replaced twice and the problem came back soon. Then it would mean that both replacements were taken from the same defective batch?
2) the iBooster ticking problem was typical to 2014 Tesla, however at speeds above 25 mph. For some owners their dealers also went with the booster replacement. However in January 2015 Tesla issued a software/firmware update 2.2.115 and the ticking disappeared (the link in here).
3) another Bolt owner told that besides i=Booster replacement his dealer did as well some update. Nobody else in the Bolt/Volt forums told that or nobody knew they received an update.
As for having the same problem twice, there was at least one Bolt owner who had two defective traction battery packs replaced...stuff happens.

The clicking in Bolts appears to happen at rest, rather than while moving, as in the Tesla cases. But if it is a software problem, god help us. GM is not a Silicon Valley tech company. ?
 

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Update regarding the assumption on the master cylinder piston not in home position.

I've read the brake booster control unit sensors using GDS2. Both the input and output rods are at exactly "0" position, which means at home position. What theoretically might be causing the problem - the other two parameters.

Brake Pedal Position Calculated from Input Rod Position Sensor 1 which is very very slighly above zero at 0.006in.
Brake Pedal Position Calculated from Input Rod Position Sensor 2 shows 0.0087in.

I succeded to achieve a perfect zero for Brake Pedal Position Calculated from Input Rod Position Sensor 1, but the ticking from the booster still there.

I reached the Chevy dealership and shared with them all the info I have. Will see if they will be able to support my troubleshooting distantly (I'm in Europe).

As well I reached Bosch central office in Germany, they promised to come back to me after their investigation on the potentially failing iBooster. I asked them to look to their records. I hope Chevrolet has reported to Bosch about a number of replacements they've been doing.
 

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The clicking in Bolts appears to happen at rest, rather than while moving
In my Volt it happens at rest too. As well I can hear it in some intervals when moving up to 20mi/h speed. I guess it is always there simply I do not hear it later anymore because other noises (wind and tires) are more loud.
 
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